From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760018AbYD2M6W (ORCPT ); Tue, 29 Apr 2008 08:58:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758537AbYD2M6G (ORCPT ); Tue, 29 Apr 2008 08:58:06 -0400 Received: from e28smtp04.in.ibm.com ([59.145.155.4]:43813 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757540AbYD2M6E (ORCPT ); Tue, 29 Apr 2008 08:58:04 -0400 Date: Tue, 29 Apr 2008 18:27:50 +0530 From: Gautham R Shenoy To: linux-kernel@vger.kernel.org, Zdenek Kabelac , Peter Zijlstra , Oleg Nesterov , Heiko Carstens , "Rafael J. Wysocki" Cc: Andrew Morton , Ingo Molnar , Srivatsa Vaddagiri Subject: [PATCH 1/8] lockdep: fix recursive read lock validation Message-ID: <20080429125750.GB23562@in.ibm.com> Reply-To: ego@in.ibm.com References: <20080429125659.GA23562@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080429125659.GA23562@in.ibm.com> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Subject: lockdep: fix recursive read lock validation From: Peter Zijlstra __lock_acquire( .read = 2 ) hlock->read = read; /* [1] */ validate_chain() ret = check_deadlock(); /* returns 2 when recursive */ if (ret == 2) hlock->read = 2; /* but it was already 2 from [1] */ check_prevs_add() if (hlock->read != 2) /* add to dependency chain */ So it will never add a recursive read lock to the dependency chain. Fix this by setting hlock->read to 1 when its the first recursive lock instance. This means that the following sequence is now invalid, whereas previously it was considered valid: rlock(a); rlock(b); runlock(b); runlock(a) rlock(b); rlock(a); It really is invalid when considered against write locks. Signed-off-by: Peter Zijlstra Signed-off-by: Gautham R Shenoy --- kernel/lockdep.c | 9 ++++----- lib/locking-selftest.c | 12 ++++++------ 2 files changed, 10 insertions(+), 11 deletions(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 81a4e4a..94b0f4f 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -1556,12 +1556,11 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock, if (!ret) return 0; /* - * Mark recursive read, as we jump over it when - * building dependencies (just like we jump over - * trylock entries): + * If we are the first recursive read, don't jump over our + * dependency. */ - if (ret == 2) - hlock->read = 2; + if (hlock->read == 2 && ret != 2) + hlock->read = 1; /* * Add dependency only if this lock is not the head * of the chain, and if it's not a secondary read-lock: diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 280332c..c84a689 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -1135,12 +1135,12 @@ void locking_selftest(void) debug_locks_silent = !debug_locks_verbose; DO_TESTCASE_6R("A-A deadlock", AA); - DO_TESTCASE_6R("A-B-B-A deadlock", ABBA); - DO_TESTCASE_6R("A-B-B-C-C-A deadlock", ABBCCA); - DO_TESTCASE_6R("A-B-C-A-B-C deadlock", ABCABC); - DO_TESTCASE_6R("A-B-B-C-C-D-D-A deadlock", ABBCCDDA); - DO_TESTCASE_6R("A-B-C-D-B-D-D-A deadlock", ABCDBDDA); - DO_TESTCASE_6R("A-B-C-D-B-C-D-A deadlock", ABCDBCDA); + DO_TESTCASE_6("A-B-B-A deadlock", ABBA); + DO_TESTCASE_6("A-B-B-C-C-A deadlock", ABBCCA); + DO_TESTCASE_6("A-B-C-A-B-C deadlock", ABCABC); + DO_TESTCASE_6("A-B-B-C-C-D-D-A deadlock", ABBCCDDA); + DO_TESTCASE_6("A-B-C-D-B-D-D-A deadlock", ABCDBDDA); + DO_TESTCASE_6("A-B-C-D-B-C-D-A deadlock", ABCDBCDA); DO_TESTCASE_6("double unlock", double_unlock); DO_TESTCASE_6("initialize held", init_held); DO_TESTCASE_6_SUCCESS("bad unlock order", bad_unlock_order); -- Thanks and Regards gautham